Onchidium

Onchidium is a genus of air-breathing sea slugs, shell-less marine pulmonate gastropod mollusks in the family Onchidiidae.

==Species== Some authors recognize only four species in the genus. The World Register of Marine Species lists six species as accepted. Onchidium melakense Dayrat & Goulding, 2019 Onchidium multiradiatum C. Semper, 1882 Onchidium nebulosum C. Semper, 1880 Onchidium reevesii (J. E. Gray, 1850) Onchidium stuxbergi (Westerlund, 1883) Onchidium typhae Buchannan, 1800 Onchidium multinotatum, originally described within the genus in 1883, is regarded as a nomen dubium.